Nineteen weeks is still young to be laying. I have had hens not start until nearly a year old. A lot depends on what breed or breeds you have as well.
Brahma for example are a large slow growing bird so tend to lay closer to 8 months old while a leghorn is a light fast growing chicken so tend to lay closer to 5 or 6 months old.
Patience my friend, patience.
I'm so glad to see this. I obtained a Light Brahma and a Buff Orpington about 5 weeks ago and was told both are 6 months old. The BO started laying a couple of weeks ago, but so far nothing from the Brahma. I was worried she may be defective, but now I feel like she might just need more time.